Question

calculate the molal elevation constant of water ,latent heat of vapourisation of watrr is 540 cal/g​

Answer 1

The expression for the molal elevation constant is k

b

=

L

v

0.002(T

b

o

)

2

Here, T

b

o

is the boiling point of pure solvent and L

v

is the latent heat of vaporization in cal/g of the pure solvent. It is equal to 9.72 kcal mol

−1

or 540 cal/g.

∴k

b

=

540

0.002×(373.15)

2

=0.515 K kg mol

−1

Th depression in freezing point is ΔT

b

=k

b

×m=0.515×0.1=0.0515

The boiling point is T

b

=373.15+0.0515≈373.20 K